Space within devices, e.g., compact mobile electronic devices, is often as a premium. For example, in a handheld electronic device, such as a cellular phone or a digital music player, the amount of space available to house a speaker with a backvolume may be limited.
As will be appreciated by those skilled in the art, a backvolume is included in an acoustic module or speaker arrangement, and includes sealed air trapped substantially behind a diaphragm. The size of a backvolume has a direct affect on the natural frequency of an acoustic module. In general, a larger backvolume, or a backvolume that traps a relatively large volume of air, has a lower natural frequency and a fuller sound than a smaller backvolume, or a backvolume that traps a relatively small volume of air.
A backvolume is typically sealed to a speaker box of an acoustic module or speaker arrangement. For example, a backvolume may be enclosed in a box that is sealed against a speaker box such that a minimal amount of air leaks from the backvolume. Increasing the size of a backvolume of an acoustic module, or increasing an air volume associated with a backvolume, lowers the natural frequency of the acoustic module and improves the fullness of the sound produced by the acoustic module. However, as space available in a small mobile device in which an acoustic module is contained is often relatively limited, it is generally difficult to increase the size of a backvolume.
A backvolume may be enclosed in an injection molded box formed from a plastic material. Although the size of a backvolume may be increased by decreasing the thickness of an injection molded box that encloses the backvolume, decreasing the thickness of an injection molded box may adversely affect the structural integrity of the injection molded box and, thus, cause the injection molded box to lose its shape. Additionally, an injection molding process may be compromised due to the difficulties associated with flowing a material into a mold arranged to create a relatively thin box. A thinner injection molded box may be at risk of cracking, and may be difficult to seal to a speaker box. Further, not all shapes may be injection molded and, as such, may utilize complex sealed joints which require extra wall thickness, and may have yield and reliability risk.
Therefore, there is a need for constructing an enclosure for a backvolume of an acoustic module or speaker arrangement that substantially enlarges available volume of the backvolume in compact mobile electronic devices without compromising the integrity of the acoustic module or speaker arrangement.